Direct current, low frequency, and digital circuits are often tested using a high impedance voltage probe or a low impedance current probe; however, such testing probes cannot be used to test all electromagnetic energy circuits. For example, microwave circuits are not typically tested in this fashion.
Microwave test equipment typically measures power. In order to test a microwave circuit, each microwave component is typically presented with a matched load and source. When knowledge of intercircuit performance is desired in a complex microwave circuit, test ports may be designed into the circuit. Alternatively, the microwave circuit may be tested a partial assembly.
When test ports are designed into the circuit, valuable circuit real estate is used. Further, the determination of the critical circuit junction to place an observation point is often difficult.
When a fault exists in a circuit, it may be desirable to disassemble the circuit into subassemblies in order to locate the fault; however, through the disassembly of the circuit (or the re-assembly), the fault could get lost (or even never located). This is particularly problematic in the case of testing space hardware, where if the fault is lost during troubleshooting (including disassembly) the circuit may be deemed not worthy for flight.
As such, it would be desirable to develop an apparatus and method for testing microwave and other high frequency circuits in an impedance matched and reliable manner that overcomes the above-mentioned deficiencies.